This paper discusses accidents on the Auckland Harbour Bridge in New Zealand, and the safety and cost-effectiveness of a moveable lane barrier installed on the bridge in November 1990. During the period 1984-88, there were 128 injury accidents on the bridge and its approaches; the most serious accidents were head-on collisions (16%), in five of which ten people were killed. In 1988, an investigation of a possible moveable barrier on the bridge began, to consider: (1) barrier design features; (2) barrier placement and weight; (3) barrier impact characteristics; (4) lane width and traffic capacity; (5) end treatment; (6) barrier systems operation; (7) operation and maintenance issues; (8) environmental environmental factors; and (9) implementation costs and timetable. The proposed system was proved to be technically sound and safe. The eventual design used a 2km long barrier, consisting of a continuous chain of 2000 1m long concrete block units that are hinged together. The barrier is shifted by a self-propelled transfer vehicle, to cater for morning and evening peak traffic flows in opposite directions. The project's benefit-cost is 6.8. The barrier has been a most effective safety measure, while maintaining tidal flow operations.
Abstract